Conventionally, techniques (optical IP techniques) for establishing paths, i.e., TDM (Time Division Multiplexing) channels and wavelengths, by signaling protocols which can be activated in an IP (Internet Protocol) layer have been developed. For the optical IP network models using these techniques, two models, i.e., (1) a peer model represented by prior art document 1, and (2) an overlay model represented by an OIF-UNI (see prior art document 2), have been proposed.
In the peer model in (1), IP addresses, existing in a same address space as external IP networks being connected to an optical network, are used. The peer model is characterized in that a device, i.e., an optical cross connect, can be acknowledged as a node by external IP networks. Therefore, multi-layer cooperative functions, i.e., designating optical paths by using the external IP networks, and establishing the optical paths cooperatively with routing protocols in the external IP networks, can be realized easily.
However, the addresses existing in the same space as the external IP networks are used for controlling the optical paths; therefore, there is a problem in containing a plurality of external IP networks in an optical network.
In the overlay model in (2), an address space for the optical network and an address space for the external IP networks contained there, are independent completely; therefore, topologies and addresses in the optical network are invisible to external IP networks. Therefore, in contrast to the peer model, it is characterized in that, providing multi-layer cooperative functions is difficult, but that it is easy to contain a plurality of networks. Also, in general, in the overlay mode, information regarding paths between the external IP networks are exchanged by passing the routing protocols in the established optical paths; thus, it is necessary to establish/release neighborhood relationships each time the optical paths are established/released. If the neighborhood relationships of the routing operation change, instability increases in the external IP networks because the external IP networks acknowledge that the topologies are being changed in the network.
In general, for carriers, i.e., an applicant having a plurality of IP networks, in terms of efficient use of network resources, i.e., optical fibers, it is very important to multiplex a plurality of IP networks on a single optical network. Also, if multi-layer cooperative functions for controlling the optical paths autonomously are realized in accordance with fluctuations (i.e., updating the routing, and increasing/decreasing traffic amount) in the IP networks, it may reduce operational costs for the carriers.
In addition, if multi-layer cooperative functions are realized, the optical paths are established/released frequently. In terms of safety in the networks, it is desirable that the routing operation in the external IP networks not be affected by the fluctuations of the topologies of the optical paths.
Therefore, new optical IP network models satisfying these requirements are necessary in order to apply the optical IP techniques to backbone networks owned by carriers.
In a core network formed by conventional optical paths or layer 2 paths, an apparatus having pre-installed IP routers as an edge router has additional functions, i.e., GMPLS (for example, see prior art document 3), for setting the optical paths. There are ordinary IP connections (inter-router connections) via these paths among the edge routers. In order to realize direct communications mutually among all of the edge routers, the optical paths or the layer 2 paths must be established in the core network in a mesh manner. Therefore, if the number of the edge routers increases, the number of the paths maintained in an edge router increases; thus, the number of the IP interfaces which the edge router must have increases.
As explained above, if, in terms of scalability, the core network is a large one, the number of the IP interfaces which the edge router must have increases. In general, the IP interfaces are expensive because complicated IP processes, i.e., retrieving the IP addresses, are conducted. Also, such a complication is a bottle neck for increasing interface speeds.
On the other hand, in these core networks, the optical paths are realized by wavelength or logical connection of the layer 2; therefore, number of the connections which can be established by each apparatus is limited. For example, if the optical paths are realized by multiplexing wavelengths, there is a limit due to the number of the wavelength multiplexes in a WDM apparatus. Communication speed with respect to a wavelength is determined by the IP interface speeds in the edge router; therefore, several wavelengths are consumed unless the interface speeds improve. Accordingly, the number of the edge routers which can be contained in the core network is limited due to the limitations of the number of the wavelengths in the WDM apparatus; therefore, it is not possible to facilitate larger scale networks.
There are problems in core networks formed by conventional optical paths or the layer 2 paths in terms of architecture, cost performance, and scalability.
FIG. 11 is a schematic diagram for explaining a conventional data transmission network.
A plurality of line exchangers 3200 are connected by at least a communication line 3300; thus, a line exchange network is formed. A plurality of packet exchangers 3100 are connected to the line exchangers in this line exchange network via the communication lines 3300.
Each of the line exchangers 3200 is formed by a line switch and a section for controlling line paths.
The line switch is connected to a line switch disposed in at least other line exchanger via a plurality of communication lines.
The section for controlling line paths controls the line switch and connects two communication lines. The communication line is, i.e., an optical line, an SDH/SONET line, an ATM line, an MPLS-LSP line, or an FR line. The section for controlling line paths is connected to the line switch disposed in at least one other line exchanger via communication paths 3700 between the line exchangers. The section for controlling line paths exchanges information, i.e., the number of the communication lines for connecting and exchanging the lines mutually, via the communication lines between the line exchangers. It is possible to know the connection relationships in an entire line exchange network by using communication protocols, i.e., OSPF-TE (see prior art document 4) and PNNI (prior art document 5). FIG. 12 is a schematic view for showing connection information among the line exchangers.
Each of the packet exchangers 3100 is formed by a packet switch, a section for setting and controlling lines, and a section for controlling packet lines.
The packet switch is connected to at least the line exchanger 3200 via the communication lines 3300.
The section for setting and controlling lines is connected to at least the packet exchanger/communication lines 3600 among the line exchangers. If parties, i.e., maintenance providers, instruct the packet exchangers 3100 to set new communication lines between two random packet exchangers, the section for setting and controlling lines sends out a message to the line exchangers 3200 to set and control lines. The line exchangers 3200 having received the message for setting and controlling lines, select vacant communication lines necessary for connecting two packet exchangers in accordance with connection-related information in an entire line exchange network in the line exchange network. For example, the communication lines 3300-1-2, 3300-2-1, 3300-5-1, and 3300-4-1 are vacant lines among the packet line exchangers 3100-1 and 3100-2 in accordance with the connection-related information. If these communication lines are connected by the line switches disposed in the line exchangers 3200-1, 2, and 3, it is determined that the communication lines among the packet exchangers 3100-1 and 3100-2 are connectable. In accordance with the determination result, the message for setting and controlling lines is transmitted to other line exchangers. By repeating this, the communication lines are set among the packet exchangers; thus, it is possible to exchange packet data.
The section for controlling packet lines inserts a packet route information message into the communication lines 3300 by a packet insertion/extraction circuit. The inserted packet route information message is transmitted to at least one other section for controlling packet paths via the communication lines. By exchanging the message, it is possible to obtain the connection-related information in a packet communication network mutually. FIG. 13 is a view for showing route information of a packet exchange network. It is possible to determine the paths for transmitting packets in accordance with this route information. The packet exchange network corresponds to networks, i.e., IP packet networks. It is possible to determine the connection relationship of the packet networks and the paths for transmitting packets by using protocols, i.e., the OSPF (see prior art document 6) and the IS-IS protocol (see a prior art document 7). For example, it is determined that the packets transmitted from the packet exchanger 3100-1 to the packet exchanger 3100-3 are transmitted to the communication line 3300-1-1.
FIG. 14 is a schematic diagram for explaining a conventional data transmission network.
A plurality of line exchangers 3200 are connected by at least a communication line 3300; thus, a line exchange network is formed. A plurality of packet exchangers 3100 are connected to the line exchangers in this line exchange network via the communication lines 3300.
Each of the line exchangers 3200 is formed by a line switch and a section for controlling line/packet paths.
The line switch is connected to a line switch disposed in at least one other line exchanger via a plurality of communication lines. The section for controlling packet lines controls the line switch and connects two communication lines. The communication line is, i.e., an optical line, a SDH/SONET line, an ATM line, an MPLS-LSP line, or an FR line.
The section for controlling line/packet paths is connected to the line switch disposed in at least one other line exchanger via communication paths 3700 between the line exchangers.
Each of the packet exchangers 3100 is formed by a packet switch, and a section for controlling line/packet paths.
The packet switch is connected to at least the line exchanger 3200 via the communication lines 3300.
The section for setting and controlling lines/packets is connected to at least the line exchanger 3200 by packet exchanger/communication lines 3600 among the line exchangers.
The section for controlling line/packet path exchanges information, i.e., the number of the communication lines for connecting and exchanging the lines mutually, via the communication paths 3700 among line exchangers. In addition, by exchanging the packet route information messages, it is possible to obtain connection-related information of the packet communication network. It is possible to learn the connection relationship in the entire line exchange network by using communication protocols, i.e., OSPF-TE (see prior art document 4) and a PNNI (see a prior art document 5). Also, it is possible to learn the connection relationship in the packet network mutually by using communication protocols, i.e., the OFPF protocol and the IS-IS protocol. FIG. 15 shows the connection information of a line exchange network and an integrated packet exchange network. It is possible to determine optimum paths for transmitting packets in accordance with this information.
If parties, i.e., maintenance providers, instruct the packet exchangers to set new communication lines between two random packet exchangers, the section for controlling line/packet paths selects the communication lines for connecting two packet exchangers by using the line network information and the packet network information. For example, the communication lines 3300-1-2, 3300-2-1, 3300-5-1, and 3300-4-1 are connected by the line switches disposed in the line exchangers 3200-1, 2, and 3 among the packet exchangers 3100-1 and 3100-2. By doing this, it is determined that the communication lines among the packet exchangers 3100-1 and 3100-2 are connectable. In accordance with the determination results, a message for setting and controlling connected lines is transmitted to the other line exchangers. By repeating this, the communication lines are set among the packet exchangers; thus, it is possible to exchange packet data.
In accordance with the above explained conventional technology, the connection information of the line exchange network and the connection information of the packet exchange network are independent. Therefore, the packet exchanger cannot dispose the communication lines optimally among the packet exchangers by using the information of the line exchange network.
Also, in the other conventional technology explained above, the connection information of the line exchange network and the connection information of the packet exchange network are stored commonly; therefore, the packet exchanger can dispose the communication lines optimally by using the information of the line exchange network. However, there has been a problem in separating the packet transmission network and a network for exchanging and controlling lines in that the packets transmitted from the packet exchangers 3100-1 to 3100-3 have been transmitted to the communication path 3600-1 undesirably.
Prior Art Document 1
    Generalized Multi-Protocol Label Switching: “Generalized Multi-Protocol Label Switching Architecture”, IETF Internet-Draft, [online], May, 2003, [retrieved July, 2003], Internet<URL HYPERLINK “http://www.ietf.org//internet-drafts/draft-ietf-ccamp-gmpls-architecture-07.txt” http://www.ietforg//internet-drafts/draft-ietf-ccamp-gmpls-architecture-07.txtPrior Art Document 2    Network Interface, “User Network Interface (UNI) 1.0 Signaling Specification: Changes from OIF200.125.5”, The Optical Internetworking Forum, Contribution Number: OIF2000.125.7Prior Art Document 3    Generalized MPLS-Signaling Functional Description, IETF, [online], August 2002, [retrieved December 2002], Internet “URL:http://www.ietf.org/internet-drafts/draft-ietf-mpls-generalized-signaling-09.txt”Prior Art Document 4    IETF, “OSPF Extensions in Support of Generalized MPLS”, K. K ompella (Editor), Y. Rekhter (Editor), Juniper Networks, December 2002, [online], [retrieved May 23, H-15], Internet “http://www.ietf, org/internet-drafts/draft-ietf-ccamp-ospf-gmpls-extensions-09.txt”Prior Art Document 5    ATM Forums “Private Network-Network interface Specification Version1.1(PNNI 1.1)”, April 2002, [online], retrieved May 23, H15], Internet “ftp://ftp.atmforum.com/pub/approved-specs/af-pnni-0055.001.pdf”Prior Art Document 6    IETF, “OSPF Version 2, RFC2328”, J. Moy, Ascend Communications, Inc., April 1998[online], [retrieved May 23, H15], Internet internet “ftp://ftp.rfc-editor.org/in-notes/rfc2328.txt”Prior Art Document 7    ISO, “Intermediate System to Intermediate System, DP 10589”